Package it.unimi.di.big.mg4j.index.cluster

Class ContiguousDocumentalStrategy

java.lang.Object

it.unimi.di.big.mg4j.index.cluster.ContiguousDocumentalStrategy

All Implemented Interfaces:

ClusteringStrategy, DocumentalClusteringStrategy, DocumentalPartitioningStrategy, PartitioningStrategy, Serializable

public class ContiguousDocumentalStrategy
extends Object
implements DocumentalPartitioningStrategy, DocumentalClusteringStrategy, Serializable

A documental partitioning and clustering strategy that partitions an index into contiguous segments.

To partition an index in contiguous parts, you must provide an array of cutpoints, which define each part. More precisely, given cutpoints c₀,c₂,…,c_k, the global index will be partitioned into k local indices containing the documents from c₀ (included) to c₁ (excluded), from c₁ (included) to c₂ and so on. Note that necessarily c₀=0 and c_k=N, where N is the number of globally indexed documents.

The properties() method provides two properties, pointerfrom and pointerto, that contain the first (included) and last (excluded) pointer in the local index.

Author:

Alessandro Arrabito, Sebastiano Vigna

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor	Description
ContiguousDocumentalStrategy(long... cutPoint)	Creates a new contiguous strategy with the given cutpoints.

Method Summary

Modifier and Type	Method	Description
long	globalPointer(int localIndex, long localPointer)	Returns the global document pointer given a local index and a local document pointer.
int	localIndex(long globalPointer)	Returns the index to which a given global document pointer is be mapped by this strategy.
long	localPointer(long globalPointer)	Returns the local document pointer corresponding to a global document pointer.
long	numberOfDocuments(int localIndex)	Returns the number of documents that will be assigned to the given local index.
int	numberOfLocalIndices()	Returns the number of local indices created by this strategy.
Properties[]	properties()	Returns an array of properties, one for each local index, that specify additional information about local indices.
String	toString()

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

ContiguousDocumentalStrategy

public ContiguousDocumentalStrategy(long... cutPoint)

Creates a new contiguous strategy with the given cutpoints.

Note that DocumentalStrategies has ready-made factory methods for the common cases.

Parameters:

cutPoint - an array of cutpoints (see the class description}.

Method Detail

numberOfLocalIndices

public int numberOfLocalIndices()

Description copied from interface: PartitioningStrategy

Returns the number of local indices created by this strategy.

Specified by:

numberOfLocalIndices in interface ClusteringStrategy

Specified by:

numberOfLocalIndices in interface PartitioningStrategy

Returns:

the number of local indices created by this strategy.

localIndex

public int localIndex(long globalPointer)

Description copied from interface: DocumentalPartitioningStrategy

Returns the index to which a given global document pointer is be mapped by this strategy.

Specified by:

localIndex in interface DocumentalPartitioningStrategy

Parameters:

globalPointer - a global document pointer.

Returns:

the corresponding local index.

localPointer

public long localPointer(long globalPointer)

Description copied from interface: DocumentalPartitioningStrategy

Returns the local document pointer corresponding to a global document pointer.

Specified by:

localPointer in interface DocumentalClusteringStrategy

Specified by:

localPointer in interface DocumentalPartitioningStrategy

Parameters:

globalPointer - a global document pointer.

Returns:

the corresponding local document pointer.

globalPointer

public long globalPointer(int localIndex,
                          long localPointer)

Description copied from interface: DocumentalClusteringStrategy

Returns the global document pointer given a local index and a local document pointer.

Specified by:

globalPointer in interface DocumentalClusteringStrategy

Parameters:

localIndex - the local index.

localPointer - the local document pointer in localIndex.

Returns:

the global document pointer.

numberOfDocuments

public long numberOfDocuments(int localIndex)

Description copied from interface: DocumentalPartitioningStrategy

Returns the number of documents that will be assigned to the given local index.

Specified by:

numberOfDocuments in interface DocumentalClusteringStrategy

Specified by:

numberOfDocuments in interface DocumentalPartitioningStrategy

Parameters:

localIndex - the local index.

Returns:

the number of documents that will be assigned to localIndex.

properties

public Properties[] properties()

Description copied from interface: PartitioningStrategy

Returns an array of properties, one for each local index, that specify additional information about local indices.

Specified by:

properties in interface PartitioningStrategy

Returns:

an array of properties, one for each local index; any element can be null (in that case, the set of properties is assumed to be empty).

toString

public String toString()

Overrides:

toString in class Object